draft-ietf-6man-text-addr-representation-06.txt   draft-ietf-6man-text-addr-representation-07.txt 
IPv6 Maintenance Working Group S. Kawamura IPv6 Maintenance Working Group S. Kawamura
Internet-Draft NEC BIGLOBE, Ltd. Internet-Draft NEC BIGLOBE, Ltd.
Updates: 4291 (if approved) M. Kawashima Updates: 4291 (if approved) M. Kawashima
Intended status: Standards Track NEC AccessTechnica, Ltd. Intended status: Standards Track NEC AccessTechnica, Ltd.
Expires: August 23, 2010 February 19, 2010 Expires: August 29, 2010 February 25, 2010
A Recommendation for IPv6 Address Text Representation A Recommendation for IPv6 Address Text Representation
draft-ietf-6man-text-addr-representation-06 draft-ietf-6man-text-addr-representation-07
Abstract Abstract
As IPv6 network grows, there will be more engineers and also non- As IPv6 deployment increases there will be a dramatic increase in the
engineers who will have the need to use an IPv6 address in text. need to use IPv6 addresses in text. While the IPv6 address
While the IPv6 address architecture RFC 4291 section 2.2 depicts a architecture in RFC 4291 section 2.2 describes a flexible model for
flexible model for text representation of an IPv6 address, this text representation of an IPv6 address this flexibility has been
flexibility has been causing problems for operators, system causing problems for operators, system engineers, and users. This
engineers, and users. This document will describe the problems that document defines a canonical textual representation format. It does
a flexible text representation has been causing. This document also not define a format for internal storage, such as within an
recommends a canonical representation format that best avoids application or database. It is expected that the canonical format is
confusion. It is expected that the canonical format is followed by followed by humans and systems when representing IPv6 addresses as
humans and systems when representing IPv6 addresses as text, but all text, but all implementations must accept and be able to handle any
implementations must accept and be able to handle any legitimate legitimate RFC 4291 format.
RFC4291 format.
Status of this Memo Status of this Memo
This Internet-Draft is submitted to IETF in full conformance with the This Internet-Draft is submitted to IETF in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as Internet- other groups may also distribute working documents as Internet-
Drafts. Drafts.
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and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
The list of current Internet-Drafts can be accessed at The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt. http://www.ietf.org/ietf/1id-abstracts.txt.
The list of Internet-Draft Shadow Directories can be accessed at The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html. http://www.ietf.org/shadow.html.
This Internet-Draft will expire on August 23, 2010. This Internet-Draft will expire on August 29, 2010.
Copyright Notice Copyright Notice
Copyright (c) 2010 IETF Trust and the persons identified as the Copyright (c) 2010 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of (http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of include Simplified BSD License text as described in Section 4.e of
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2001:db8::0:1:0:0:1 2001:db8::0:1:0:0:1
2001:0db8::1:0:0:1 2001:0db8::1:0:0:1
2001:db8:0:0:1::1 2001:db8:0:0:1::1
2001:db8:0000:0:1::1 2001:db8:0000:0:1::1
2001:DB8:0:0:1::1 2001:DB8:0:0:1::1
All the above represent the same IPv6 address. This flexibility has All of the above examples represent the same IPv6 address. This
caused many problems for operators, systems engineers, and customers. flexibility has caused many problems for operators, systems
The problems will be noted in Section 3. Also, a canonical engineers, and customers. The problems are noted in Section 3.
representation format to avoid problems will be introduced in Also, a canonical representation format to avoid problems is
Section 4. introduced in Section 4.
1.1. Requirements Language 1.1. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119]. document are to be interpreted as described in [RFC2119].
2. Text Representation Flexibility of RFC4291 2. Text Representation Flexibility of RFC4291
Examples of flexibility in Section 2.2 of [RFC4291] are described Examples of flexibility in Section 2.2 of [RFC4291] are described
below. below.
2.1. Leading Zeros in a 16 Bit Field 2.1. Leading Zeros in a 16 Bit Field
'It is not necessary to write the leading zeros in an individual 'It is not necessary to write the leading zeros in an individual
field.' field.'
In other words, it is also not necessary to omit leading zeros. This Conversely it is also not necessary to omit leading zeros. This
means that, it is possible to select from such as the following means that, it is possible to select from such as the following
example. The final 16 bit field is different, but all these example. The final 16 bit field is different, but all these
addresses mean the same. addresses represent the same address.
2001:db8:aaaa:bbbb:cccc:dddd:eeee:0001 2001:db8:aaaa:bbbb:cccc:dddd:eeee:0001
2001:db8:aaaa:bbbb:cccc:dddd:eeee:001 2001:db8:aaaa:bbbb:cccc:dddd:eeee:001
2001:db8:aaaa:bbbb:cccc:dddd:eeee:01 2001:db8:aaaa:bbbb:cccc:dddd:eeee:01
2001:db8:aaaa:bbbb:cccc:dddd:eeee:1 2001:db8:aaaa:bbbb:cccc:dddd:eeee:1
2.2. Zero Compression 2.2. Zero Compression
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"::" indicates one or more groups of 16 bits of zeros.' "::" indicates one or more groups of 16 bits of zeros.'
It is possible to select whether or not to omit just one 16 bits of It is possible to select whether or not to omit just one 16 bits of
zeros. zeros.
2001:db8:aaaa:bbbb:cccc:dddd::1 2001:db8:aaaa:bbbb:cccc:dddd::1
2001:db8:aaaa:bbbb:cccc:dddd:0:1 2001:db8:aaaa:bbbb:cccc:dddd:0:1
In case where there is more than one zero fields, there is a choice In case where there is more than one zero fields, there is a choice
of how many fields can be shortened. Examples follow. of how many fields can be shortened.
2001:db8:0:0:0::1 2001:db8:0:0:0::1
2001:db8:0:0::1 2001:db8:0:0::1
2001:db8:0::1 2001:db8:0::1
2001:db8::1 2001:db8::1
In addition, [RFC4291] in section 2.2 notes, In addition, [RFC4291] in section 2.2 notes,
'The "::" can only appear once in an address.' 'The "::" can only appear once in an address.'
This gives a choice on where, in a single address to compress the This gives a choice on where in a single address to compress the
zero. Examples are shown below. zero.
2001:db8::aaaa:0:0:1 2001:db8::aaaa:0:0:1
2001:db8:0:0:aaaa::1 2001:db8:0:0:aaaa::1
2.3. Uppercase or Lowercase 2.3. Uppercase or Lowercase
[RFC4291] does not mention about preference of uppercase or [RFC4291] does not mention any preference of uppercase or lowercase.
lowercase. Various flavors are shown below.
2001:db8:aaaa:bbbb:cccc:dddd:eeee:aaaa 2001:db8:aaaa:bbbb:cccc:dddd:eeee:aaaa
2001:db8:aaaa:bbbb:cccc:dddd:eeee:AAAA 2001:db8:aaaa:bbbb:cccc:dddd:eeee:AAAA
2001:db8:aaaa:bbbb:cccc:dddd:eeee:AaAa 2001:db8:aaaa:bbbb:cccc:dddd:eeee:AaAa
3. Problems Encountered with the Flexible Model 3. Problems Encountered with the Flexible Model
3.1. Searching 3.1. Searching
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being done to see if it was not in use. This may cause problems to being done to see if it was not in use. This may cause problems to
the end-hosts or end-users. This type of address management is very the end-hosts or end-users. This type of address management is very
often seen in enterprise networks and also in ISPs. often seen in enterprise networks and also in ISPs.
3.1.3. Searching with Whois 3.1.3. Searching with Whois
The "whois" utility is used by a wide range of people today. When a The "whois" utility is used by a wide range of people today. When a
record is set to a database, one will likely check the output to see record is set to a database, one will likely check the output to see
if the entry is correct. If an entity was recorded as 2001:db8::/48, if the entry is correct. If an entity was recorded as 2001:db8::/48,
but the whois output showed 2001:0db8:0000::/48, most non-engineers but the whois output showed 2001:0db8:0000::/48, most non-engineers
would think that their input was wrong, and will likely retry several would think that their input was wrong and will likely retry several
times or make a frustrated call to the database hostmaster. If there times or make a frustrated call to the database hostmaster. If there
was a need to register the same address on different systems, and was a need to register the same address on different systems, and
each system showed a different text representation, this would each system showed a different text representation, this would
confuse people even more. Although this document focuses on confuse people even more. Although this document focuses on
addresses rather than prefixes, this is worth mentioning since addresses rather than prefixes, this is worth mentioning since the
problems encountered are mostly equal. problems encountered are mostly equal.
3.1.4. Searching for an Address in a Network Diagram 3.1.4. Searching for an Address in a Network Diagram
Network diagrams and blue-prints often show what IP addresses are Network diagrams and blueprints often show what IP addresses are
assigned to a system devices. In times of trouble shooting, there assigned to a system devices. In times of trouble shooting there may
may be a need to search through a diagram to find the point of be a need to search through a diagram to find the point of failure
failure (for example, if a traceroute stopped at 2001:db8::1, one (for example, if a traceroute stopped at 2001:db8::1, one would
would search the diagram for that address). This is a technique search the diagram for that address). This is a technique quite
quite often in use in enterprise networks and managed services. often in use in enterprise networks and managed services. Again, the
Again, the different flavors of text representation will result in a different flavors of text representation will result in a time-
time-consuming search, leading to longer MTTR in times of trouble. consuming search leading to longer MTTR in times of trouble.
3.2. Parsing and Modifying 3.2. Parsing and Modifying
3.2.1. General Summary 3.2.1. General Summary
With all the possible text representation ways, each application must With all the possible methods of text representation each application
include a module, object, link, etc. to a function that will parse must include a module, object, link, etc. to a function that will
IPv6 addresses in a manner that no matter how it is represented, they parse IPv6 addresses in a manner that no matter how it is
will mean the same address. Many system engineers who integrate represented, they will mean the same address. Many system engineers
complex computer systems to corporate customers will have who integrate complex computer systems for corporate customers will
difficulties finding that their favorite tool will not have this have difficulties finding that their favorite tool will not have this
function, or will encounter difficulties such as having to rewrite function, or will encounter difficulties such as having to rewrite
their macro's or scripts for their customers. their macros or scripts for their customers.
3.2.2. Logging 3.2.2. Logging
If an application were to output a log summary that represented the If an application were to output a log summary that represented the
address in full (such as 2001:0db8:0000:0000:1111:2222:3333:4444), address in full (such as 2001:0db8:0000:0000:1111:2222:3333:4444),
the output would be highly unreadable compared to the IPv4 output. the output would be highly unreadable compared to the IPv4 output.
The address would have to be parsed and reformed to make it useful The address would have to be parsed and reformed to make it useful
for human reading. Sometimes, logging for critical systems is done for human reading. Sometimes logging for critical systems is done by
by mirroring the same traffic to two different systems. Care must be mirroring the same traffic to two different systems. Care must be
taken that no matter what the log output is, the logs should be taken so that no matter what the log output is the logs should be
parsed so they will mean the same. parsed so they will mean the same.
3.2.3. Auditing: Case 1 3.2.3. Auditing: Case 1
When a router or any other network appliance machine configuration is When a router or any other network appliance machine configuration is
audited, there are many methods to compare the configuration audited, there are many methods to compare the configuration
information of a node. Sometimes, auditing will be done by just information of a node. Sometimes auditing will be done by just
comparing the changes made each day. In this case, if configuration comparing the changes made each day. In this case if configuration
was done such that 2001:db8::1 was changed to 2001:0db8:0000:0000: was done such that 2001:db8::1 was changed to 2001:0db8:0000:0000:
0000:0000:0000:0001 just because the new engineer on the block felt 0000:0000:0000:0001 just because the new engineer on the block felt
it was better, a simple diff will show that a different address was it was better, a simple diff will show that a different address was
configured. If this was done on a wide scale network, people will be configured. If this was done on a wide scale network people will be
focusing on 'why the extra zeros were put in' instead of doing any focusing on 'why the extra zeros were put in' instead of doing any
real auditing. Lots of tools are just plain 'diff's that do not take real auditing. Lots of tools are just plain diffs that do not take
into account address representation rules. into account address representation rules.
3.2.4. Auditing: Case 2 3.2.4. Auditing: Case 2
Node configurations will be matched against an information system Node configurations will be matched against an information system
that manages IP addresses. If output notation is different, there that manages IP addresses. If output notation is different there
will need to be a script that is implemented to cover for this. The will need to be a script that is implemented to cover for this. The
result of an SNMP GET operation, converted to text and compared to a result of an SNMP GET operation, converted to text and compared to a
textual address written by a human is highly unlikely to match on textual address written by a human is highly unlikely to match on the
first try. first try.
3.2.5. Verification 3.2.5. Verification
Some protocols require certain data fields to be verified. One Some protocols require certain data fields to be verified. One
example of this is X.509 certificates. If an IPv6 address field in a example of this is X.509 certificates. If an IPv6 address field in a
certificate was incorrectly verified by converting it to text and certificate was incorrectly verified by converting it to text and
making a simple textual comparison to some other address, the making a simple textual comparison to some other address, the
certificate may be mistakenly shown as being invalid due to a certificate may be mistakenly shown as being invalid due to a
difference in text representation methods. difference in text representation methods.
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address representation should be handled with care. Not all address representation should be handled with care. Not all
customers are engineers nor have the same skill in IPv6 technology. customers are engineers nor have the same skill in IPv6 technology.
The network operations center will have to take extra steps to The network operations center will have to take extra steps to
humanly parse the address to avoid having to explain to the customers humanly parse the address to avoid having to explain to the customers
that 2001:db8:0:1::1 is the same as 2001:db8::1:0:0:0:1. This is one that 2001:db8:0:1::1 is the same as 2001:db8::1:0:0:0:1. This is one
thing that will never happen in IPv4 because IPv4 address cannot be thing that will never happen in IPv4 because IPv4 address cannot be
abbreviated. abbreviated.
3.3.3. Abuse 3.3.3. Abuse
Network abuse is reported along with the abusing IP address. This Network abuse reports generally include the abusing IP address. This
'reporting' could take any shape or form of the flexible model. A 'reporting' could take any shape or form of the flexible model. A
team that handles network abuse must be able to tell the difference team that handles network abuse must be able to tell the difference
between a 2001:db8::1:0:1 and 2001:db8:1::0:1. Mistakes in the between a 2001:db8::1:0:1 and 2001:db8:1::0:1. Mistakes in the
placement of the "::" will result in a critical situation. A system placement of the "::" will result in a critical situation. A system
that handles these incidents should be able to handle any type of that handles these incidents should be able to handle any type of
input and parse it in a correct manner. Also, incidents are reported input and parse it in a correct manner. Also, incidents are reported
over the phone. It is unnecessary to report if the letter is an over the phone. It is unnecessary to report if the letter is an
uppercase or lowercase. However, when a letter is spelled uppercase, uppercase or lowercase. However, when a letter is spelled uppercase,
people tend to clarify that it is uppercase, which is unnecessary people tend to clarify that it is uppercase, which is unnecessary
information. information.
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When an engineer decides to change the platform of a running service, When an engineer decides to change the platform of a running service,
the same code may not work as expected due to the difference in IPv6 the same code may not work as expected due to the difference in IPv6
address text representation. Usually, a change in a platform (e.g. address text representation. Usually, a change in a platform (e.g.
Unix to Windows, Cisco to Juniper) will result in a major change of Unix to Windows, Cisco to Juniper) will result in a major change of
code anyway, but flexibility in address representation will increase code anyway, but flexibility in address representation will increase
the work load. the work load.
3.4.2. Preference in Documentation 3.4.2. Preference in Documentation
A document that is edited by more than one author, may become harder A document that is edited by more than one author may become harder
to read. to read.
3.4.3. Legibility 3.4.3. Legibility
Capital case D and 0 can be quite often misread. Capital B and 8 can Capital case D and 0 can be quite often misread. Capital B and 8 can
also be misread. also be misread.
4. A Recommendation for IPv6 Text Representation 4. A Recommendation for IPv6 Text Representation
A recommendation for a canonical text representation format of IPv6 A recommendation for a canonical text representation format of IPv6
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o 2001:db8::1p80 o 2001:db8::1p80
o 2001:db8::1#80 o 2001:db8::1#80
The situation is not much different in IPv4, but the most ambiguous The situation is not much different in IPv4, but the most ambiguous
case with IPv6 is the second bullet. This is due to the "::"usage in case with IPv6 is the second bullet. This is due to the "::"usage in
IPv6 addresses. This style is NOT RECOMMENDED for its ambiguity. IPv6 addresses. This style is NOT RECOMMENDED for its ambiguity.
The [] style as expressed in [RFC3986] SHOULD be employed, and is the The [] style as expressed in [RFC3986] SHOULD be employed, and is the
default unless otherwise specified. Other styles are acceptable when default unless otherwise specified. Other styles are acceptable when
there is exactly one style for the given context and cross-platform there is exactly one style for the given context and cross-platform
portability does not become an issue. For URIs, [RFC3986] MUST be portability does not become an issue. For URIs containing IPv6
followed. address literals, [RFC3986] MUST be followed, as well as the rules in
this document.
7. Prefix Representation 7. Prefix Representation
Problems with prefixes are just the same as problems encountered with Problems with prefixes are just the same as problems encountered with
addresses. Text representation method of IPv6 prefixes should be no addresses. The text representation method of IPv6 prefixes should be
different from that of IPv6 addresses. no different from that of IPv6 addresses.
8. Security Considerations 8. Security Considerations
This document notes on some examples where IPv6 addresses are This document notes some examples where IPv6 addresses are compared
compared in text format. The example on Section 3.2.5 is one that in text format. The example on Section 3.2.5 is one that may cause a
may cause a security risk if used for access control. The common security risk if used for access control. The common practice of
practice of comparing X.509 data is done in binary format. comparing X.509 data is done in binary format.
9. IANA Considerations 9. IANA Considerations
None. None.
10. Acknowledgements 10. Acknowledgements
The authors would like to thank Jan Zorz, Randy Bush, Yuichi Minami, The authors would like to thank Jan Zorz, Randy Bush, Yuichi Minami,
Toshimitsu Matsuura for their generous and helpful comments in kick Toshimitsu Matsuura for their generous and helpful comments in kick
starting this document. We also would like to thank Brian Carpenter, starting this document. We also would like to thank Brian Carpenter,
Akira Kato, Juergen Schoenwaelder, Antonio Querubin, Dave Thaler, Akira Kato, Juergen Schoenwaelder, Antonio Querubin, Dave Thaler,
Brian Haley, Suresh Krishnan, Jerry Huang, Roman Donchenko, Heikki Brian Haley, Suresh Krishnan, Jerry Huang, Roman Donchenko, Heikki
Vatiainen ,Dan Wing for their input. Also a very special thanks to Vatiainen ,Dan Wing, and Doug Barton for their input. Also a very
Ron Bonica, Fred Baker, Brian Haberman, Robert Hinden, Jari Arkko, special thanks to Ron Bonica, Fred Baker, Brian Haberman, Robert
and Kurt Lindqvist for their support in bringing this document to the Hinden, Jari Arkko, and Kurt Lindqvist for their support in bringing
light of IETF working groups. this document to the light of IETF working groups.
11. References 11. References
11.1. Normative References 11.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997. Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2765] Nordmark, E., "Stateless IP/ICMP Translation Algorithm [RFC2765] Nordmark, E., "Stateless IP/ICMP Translation Algorithm
(SIIT)", RFC 2765, February 2000. (SIIT)", RFC 2765, February 2000.
[RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
Resource Identifier (URI): Generic Syntax", STD 66,
RFC 3986, January 2005.
[RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing [RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing
Architecture", RFC 4291, February 2006. Architecture", RFC 4291, February 2006.
11.2. Informative References 11.2. Informative References
[I-D.ietf-behave-address-format] [I-D.ietf-behave-address-format]
Huitema, C., Bao, C., Bagnulo, M., Boucadair, M., and X. Huitema, C., Bao, C., Bagnulo, M., Boucadair, M., and X.
Li, "IPv6 Addressing of IPv4/IPv6 Translators", Li, "IPv6 Addressing of IPv4/IPv6 Translators",
draft-ietf-behave-address-format-04 (work in progress), draft-ietf-behave-address-format-04 (work in progress),
January 2010. January 2010.
[RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
Resource Identifier (URI): Generic Syntax", STD 66,
RFC 3986, January 2005.
[RFC4038] Shin, M-K., Hong, Y-G., Hagino, J., Savola, P., and E. [RFC4038] Shin, M-K., Hong, Y-G., Hagino, J., Savola, P., and E.
Castro, "Application Aspects of IPv6 Transition", Castro, "Application Aspects of IPv6 Transition",
RFC 4038, March 2005. RFC 4038, March 2005.
[RFC5214] Templin, F., Gleeson, T., and D. Thaler, "Intra-Site [RFC5214] Templin, F., Gleeson, T., and D. Thaler, "Intra-Site
Automatic Tunnel Addressing Protocol (ISATAP)", RFC 5214, Automatic Tunnel Addressing Protocol (ISATAP)", RFC 5214,
March 2008. March 2008.
Appendix A. For Developers Appendix A. For Developers
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